Exhaust System for Internal Combustion Engines

ABSTRACT

A dynamic exhaust system including a down-pipe ( 1 ) to receive exhaust gases from the engine and delivering the gases to an exhaust pipe ( 3 ). The system further includes a valve member ( 11 ) with one end extending through the exhaust pipe inlet and into the down-pipe ( 1 ). The valve ( 11 ) is movable to reduce or increase the area of the inlet port ( 2 ) of the exhaust pipe ( 3 ).

This invention relates to exhaust systems for vehicles powered by internal combustion engines.

Increasingly there is a need to control exhaust emissions of internal combustion engines to reduce the emission into the atmosphere of harmful gases and to improve fuel efficiency. While striving to achieve these objectives manufacturers are also seeking to improve power outputs through improved performance.

Legislation to control exhaust emissions of cars and lorries has already been implemented in many countries. This legislation will inevitably be extended to embrace internal combustion engine powered motor cycles and other vehicles in the next year or two.

The present invention sets out to provide a dynamic exhaust system in which the performance of the exhaust system is matched to the volume and pressure of gases exhausted from the engine to ensure more complete combustion of fuel thereby to reduce harmful emissions from the vehicle's exhaust system.

In one aspect, the invention provides a dynamic exhaust system for a vehicle powered by an internal combustion engine, the exhaust system comprising a down-pipe connected to receive exhaust gases from the engine and to deliver these gases to an exhaust pipe having at one end an inlet port for receiving the exhaust gases from the down-pipe and at its other end an outlet port for delivering exhaust gases to atmosphere, a valve member positioned at least partially within the exhaust pipe with one end extending through the inlet port and into the down-pipe, and means operable to bias the valve member towards the down-pipe, the valve member being so shaped that movement of it towards the down-pipe progressively reduces the area of the inlet port, and movement of the valve member towards the outlet port increases the area of the inlet port.

In a preferred embodiment the valve member has a generally conical nose whose cross-sectional area decreases in a direction towards the down-pipe of the internal combustion engine.

The valve member may be biased towards the inlet port by a spring, typically a coil spring.

One or more hollow baffle pods may be positioned within the exhaust pipe to define a flow passageway for exhaust gases passing through the exhaust pipe, the or each baffle pod comprising a casing formed with a plurality of apertures through which exhaust gases can pass. Where two or more baffle pods are employed, at least one may include sound-deadening material.

The or each baffle pod may comprise an apertured inner drum assembled within an outer drum with sound deadening material optionally provided between the outer surface of the inner drum and the inner surface of the outer drum.

The spring may be positioned between the end face of the valve member positioned within the exhaust pipe and the opposed surface of the baffle pod closest to the inlet port. Alternatively, the spring may be positioned between a stop positioned at or close to the outlet port of the exhaust pipe and an end face of the baffle pod closest to that stop.

The valve member may be produced from stainless steel, titanium or other like material. The baffle pods may be produced from stainless steel and the coil spring may comprise case hardened sprung steel.

The invention will now be described by way of example only with reference to the accompanying diagrammatic drawings, in which:—

FIG. 1 is a side view partly in section of a first embodiment of an exhaust system in accordance with the invention.

FIG. 2 is a side view partly in section of a second embodiment of an exhaust system in accordance with the invention;

FIG. 3 is a side view partly in section of a third embodiment of an exhaust system in accordance with the invention; and

FIGS. 4 a to 4 c illustrate assembly of a baffle pod which forms part of the illustrated exhaust systems.

The exhaust system shown in FIG. 1 comprises a down-pipe 1 (only the end section of which is shown) which is connected to receive exhaust gases from an internal combustion engine (not shown) and which communicates through an inlet port 2 with an exhaust pipe 3 of the vehicle powered by the engine. The exhaust pipe includes an outlet port 4 through which exhaust gases leave the pipe and pass to the atmosphere.

A series of abutting or neighbouring hollow baffle pods 5 are positioned within the interior of the exhaust pipe 3. These are spaced from the internal surface of the exhaust pipe to define an annular passageway 6 for the flow of exhaust gases. Each pod comprises a shell 7 of stainless steel formed with a plurality of slots 8 through which exhaust gases are able to enter the annular passageway 6. Some or all of the pods include heat resistant sound-deadening material. Exhaust gases passing through the slots 8 and into the passageway 6 significantly reduce vibrations which would otherwise occur in the exhaust pipe casing thereby reducing the level of noise generated during use of the vehicle.

The diameter of the exhaust pipe is generally larger than that of a conventional exhaust pipe to accommodate the baffle pods. Typically, the diameter is around 30% larger than that of a conventional vehicle.

The baffle pods locate within the exhaust pipe and provide a seat for one end of a coil spring 10. A valve member 11 is secured to the other end of the spring. The valve member has a nose 12 which is generally of conical shape and protrudes into and through the inlet port of the exhaust pipe and into the down pipe 1. The spring biases the valve member in a direction towards the down-pipe and the shaping of the valve member is such that movement of the nose towards the down-pipe progressively reduces the area of the inlet port; conversely, movement of the valve member away from the down-pipe produces a progressive increase in inlet port area.

A quantity of heated air passing through the passageway 6 is recycled to the inlet of the vehicle engine through conduit 9 to assist starting and early running of the engine.

The embodiment illustrated in FIG. 2 (in which like integers to those shown in FIG. 1 have the same reference numerals) is similar to that of FIG. 1 excepting that the valve member is carried by the leading baffle pod with the spring positioned between an end stop member 14 and the opposed surface of the rearmost baffle pod. In this embodiment therefore the baffle pods are movable with the valve member.

Two positions of the valve member can be seen from FIGS. 1 and 2 of the drawings. FIG. 1 shows the valve member in the position adopted when the engine is running at low revolutions and FIG. 2 shows the valve member when the internal combustion engine is operating at high revolutions. It will be seen that the effective area of the inlet port 2 is greater when the engine is operating at higher revolutions, the valve having been displaced away from the down-pipe by the pressure and volume of exhaust gases leaving the engine. At low revolutions, the effective area of the inlet port is reduced because the pressure and volume of exhaust gases is lower. Thus, the exhaust system provides a dynamic control which effectively balances the flow through the exhaust system in line with the dynamic requirements of the engine to maintain a required back pressure at the inlet port 2.

In operation, the exhaust gases passing through the down-pipe act against the valve nose 12 to control the position of the valve member within the inlet port 2 and the effective area of the inlet port. In this way the flow of gases into and through the exhaust pipe is balanced in relation to the volume and pressure of gases leaving the internal combustion engine.

The exhaust system illustrated in FIG. 3 differs from that of FIG. 1 in that the conical valve 12 includes a central bore 15 and that the baffle pods 5 define a relatively close fit within the casing 3 of the exhaust pipe. In this embodiment, therefore, no or only a limited flow of exhaust gases pass between the opposed surfaces of the pods 5 and the exhaust pipe casing. Gases will still flow through the slots 8 to damp vibrational forces which would otherwise occur in the exhaust pipe casing.

Turning now to FIG. 4, the three drawings illustrate assembly of a pod 5 by insertion of an inner drum 16 including the slots 8 into an outer drum 17 which locates within the exhaust pipe. Heat resistant sound-deadening wadding is placed between the opposed surfaces of the drums 16 and 17.

The pods 5 are used essentially for noise inhibition purposes. Where noise is not a consideration, one of the exhaust systems discussed could be used with no pods, or a limited number of pods.

The valve member is typically produced from a stainless steel or a titanium compound and the coil spring is typically produced from case hardened sprung steel.

It will be appreciated that the foregoing is merely exemplary of exhaust systems in accordance with the invention and that modifications can readily be made thereto without departing from the true scope of the invention. 

1. A dynamic exhaust system for a vehicle powered by an internal combustion engine, the exhaust system comprising a down-pipe connected to receive exhaust gases from the engine and to deliver these gases to an exhaust pipe having at one end an inlet port for receiving the exhaust gases from the down-pipe and at its other end an outlet port for delivering exhaust gases to atmosphere, a valve member positioned at least partially within the exhaust pipe with one end extending through the inlet port and into the down-pipe, and means operable to bias the valve member towards the down-pipe, the valve member being so shaped that movement of it towards the down-pipe progressively reduces the area of the inlet port, and movement of the valve member towards the outlet port increases the area of the inlet port.
 2. A system according to claim 1, wherein the valve member has a generally conical nose whose cross-sectional area decreases in a direction towards the down-pipe of the internal combustion engine.
 3. A system according to claim 1, wherein the valve member is biased towards the inlet port by a spring.
 4. A system according to claim 3 wherein the spring is a coil spring.
 5. A system according to claim 1, wherein one or more hollow baffle pods are positioned within the exhaust pipe to define a flow passageway for exhaust gases passing through the exhaust pipe, the or each baffle pod comprising a casing formed with a plurality of apertures through which exhaust gases can pass.
 6. A system according to claim 5 wherein at least one baffle pod includes sound-deadening material.
 7. A system according to claim 6, wherein the or each baffle pod comprises an apertured inner drum assembled within an outer drum.
 8. A system according to claim 7, wherein the sound deadening material is provided between the outer surface of the Inner drum and the inner surface of the outer drum.
 9. A system according to claim 1, wherein the spring is positioned between the end face of the valve member positioned within the exhaust pipe and the opposed surface of the baffle pod closest to the inlet port.
 10. A system according to claim 1, wherein the spring is positioned between a stop positioned at or close to the outlet port of the exhaust pipe and an end face of the baffle pod closest to that stop.
 11. A system according to claim 1, wherein the valve member is produced from stainless steel.
 12. A system according to claim 1, wherein the valve member is produced from titanium or other like material.
 13. A system according to claim 1, wherein the or each baffle pod is produced from stainless steel.
 14. A system according to claim 1, wherein the coil spring comprises case hardened sprung steel.
 15. (canceled) 